Actin-microtubule cytoskeletal interplay mediated by MRTF-A/SRF signaling promotes dilated cardiomyopathy caused by LMNA mutations

Mutations in the lamin A/C gene (LMNA) cause dilated cardiomyopathy associated with increased activity of ERK1/2 in the heart. We recently showed that ERK1/2 phosphorylates cofilin-1 on threonine 25 (phospho(T25)-cofilin-1) that in turn disassembles the actin cytoskeleton. Here, we show that in muscle cells carrying a cardiomyopathy-causing LMNA mutation, phospho(T25)-cofilin-1 binds to myocardin-related transcription factor A (MRTF-A) in the cytoplasm, thus preventing the stimulation of serum response factor (SRF) in the nucleus. Inhibiting the MRTF-A/SRF axis leads to decreased α-tubulin acetylation by reducing the expression of ATAT1 gene encoding α-tubulin acetyltransferase 1. Hence, tubulin acetylation is decreased in cardiomyocytes derived from male patients with LMNA mutations and in heart and isolated cardiomyocytes from Lmnap.H222P/H222P male mice. In Atat1 knockout mice, deficient for acetylated α-tubulin, we observe left ventricular dilation and mislocalization of Connexin 43 (Cx43) in heart. Increasing α-tubulin acetylation levels in Lmnap.H222P/H222P mice with tubastatin A treatment restores the proper localization of Cx43 and improves cardiac function. In summary, we show for the first time an actin-microtubule cytoskeletal interplay mediated by cofilin-1 and MRTF-A/SRF, promoting the dilated cardiomyopathy caused by LMNA mutations. Our findings suggest that modulating α-tubulin acetylation levels is a feasible strategy for improving cardiac function.


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All studies must disclose on these points even when the disclosure is negative. Reporting for specific materials, systems and methods All data generated or analysed during this study are included in this published article (and its supplementary information files). The Affymetrix microarray data generated in this study have been deposited in Gene Expression Omnibus database under accession code GSE218891.
No sex and gender analysis were performed The subjects were a 23-year-old man with cardiomyopathy associated with muscular dystrophy carrying LMNA p.delK261 mutation, a 53-year-old man with cardiomyopathy carrying LMNA p.E33D mutation and a 47-year-old woman with cardiomyopathy carrying LMNA p.R60G mutation. Control human heart samples were obtained from a 57-year-old man with an intracranial bleed, a 15-year-old woman who died of a drug overdose and a 46-year-old man who died from end-stage liver disease Sections of explanted hearts from human subjects with LMNA mutations were obtained without identifiers from Myobank-AFM de l'lnstitut de Myologie.
Myobank-AFM received approval from the French Ministry of Health and from the Committee for Protection of Patients to share tissues and cells of human origin for scientific purposes, ensuring the donors' anonymity, respect of their volition and consent according to the legislation.
Sample sizes were determined based on established practice and according to accepted standards in the field (at least 3 independent experiments in vitro and at least 3 mice for each group). These sample sizes have been shown to be sufficient to evaluate effects of Tubastatin A (Osseni, A et al., 2022;d'Ydewalle, C et al, 2011). Individual data points are shown in each figure or described in the figure legend. Microarray analysis was performed with 3 individuals as it is typical for transcriptomic analysis.All experiments were repeated at least three times independently to ensure reproducibility.
No data were excluded from analysis All experiments were repeated three times, unless indicated in the figure legend or methods. All attempts at replication were successful and actual n values are indicated in the text for all experiments.
All mice were randomly assigned to groups. For cell culture experiments, cells were split, plated, and then treated with DMSO or molecules in a randomized manner.
Many of the experiments were independently conducted by multiple authors. Echocardiographer and electrocardiographer were blinded regarding the genotype and the treament of mice. All image processing studies were analyzed in a blinded-manner by Zoheir Guesmia.